Combat vehicles are highly mobile, manned, protected, ground weapon systems designed and intended for an active, offensive combat role on the land battlefield. They are employed in direct contact with the enemy or, as in the case of artillery, in close support of the ground battle. However, when such combat vehicles are employed directly in the ground battle or immediately to the rear thereof, they are subject, with little or no warning, to engagement with hostile aircraft. Since such vehicles may find themselves engaged in direct, close combat, they must be equipped to engage in battle in any environment.
In the event an enemy resorts to the offensive use of radiological and chemical agents, such vehicles must be provided with an environmental protection system to enhance survivability under conditions of nuclear, biological and chemical warfare. An optimum system for combat vehicles is the hybrid collective protection concept which combines a positive pressure, pollutant-free environment within the crew compartment with individual crewman protective equipment, together with appropriate detector and alarm devices. Individual equipment, for example, suits, gloves, boots and a ventilated facepiece is to be used when by necessity hatches must be opened in a hostile environment. Otherwise, the crew compartment collective protection will permit the crew to operate with hatches closed without the degrading influences of face masks, gloves and boots.